The biological functions of the epitranscriptomic modification N 6 -methyladenosine (m 6 A) in plants are not fully understood. CPSF30-L is a predominant isoform of the polyadenylation factor CPSF30 and consists of CPSF30-S and an m 6 A-binding YTH domain. Little is known about the biological roles of CPSF30-L and the molecular mechanism underlying its m 6 A-binding function in alternative polyadenylation. Here, we characterized CPSF30-L as an Arabidopsis m 6 A reader whose m 6 A-binding function is required for the floral transition and abscisic acid (ABA) response. We found that the m 6 A-binding activity of CPSF30-L enhances the formation of liquid-like nuclear bodies, where CPSF30-L mainly recognizes m 6 A-modified far-upstream elements to control polyadenylation site choice. Deficiency of CPSF30-L lengthens the 3 0 untranslated region of three phenotypes-related transcripts, thereby accelerating their mRNA degradation and leading to late flowering and ABA hypersensitivity. Collectively, this study uncovers a new molecular mechanism for m 6 A-driven phase separation and polyadenylation in plants.

The recent development of ultrashort laser pulses allows for optical control of structural and electronic properties of complex quantum materials. The layered transition-metal dichalcogenide MoTe 2 , which can crystallize into several different structures with distinct topological and electronic properties, provides possibilities to control or switch between different phases. In this study, we report a photoinduced subpicosecond structural transition between the type-II Weyl semimetal phase and normal-semimetal phase in bulk crystalline MoTe 2 by using ultrafast pump-probe and time-resolved second-harmonic-generation spectroscopy. The phase transition is most clearly characterized by the dramatic change of the shear oscillation mode and the intensity loss of second-harmonic generation. This work opens up new possibilities for ultrafast manipulation of the topological properties of solids, enabling potentially practical applications for a topological switch device with ultrafast excitations.

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We use time-domain terahertz spectroscopy to measure the low energy conductivity and magnons in RuCl 3 under external magnetic field. At zero field, an oscillation with a frequency of 0.62 THz is clearly observed in time-domain spectrum below T N , which is identified as a magnon excitation in the magnetic order state. The magnon excitation is not affected by the external magnetic field H DC when it is applied along the c-axis, but is clearly suppressed when H DC is applied within ab plane. More interestingly, when the magnetic component of THz wave h(t) is perpendicular to the applied in-plane magnetic field, we observe another coherent oscillation at slightly higher energy scale at the field above 2 T, which is eventually suppressed for H DC >5 T. The measurement seems to indicate that the in-plane magnetic field can lift the degeneracy of two branches of low energy magnons at Γ point. The low energy optical conductivity calculated from the measured transmission spectrum is dominated by a broad continuum contribution, which is not affected by changing either temperature or external magnetic field. The continuum is likely to be related to the fractional spin excitation due to dominated Kitaev interaction in the material.